1. Field of the Invention
The present invention relates to a process for producing a styrenic polymer and copolymer. More particularly, it pertains to a process for efficiently producing a phenylstyrenic polymer, silicon-containing group-substituted styrenic polymer and copolymer thereof by the use of a specific catalyst.
2. Description of the Related Arts
Heretofore, styrenic polymers produced by the radical polymerization method have been molded to various shapes by various molding methods and widely used as domestic electrical appliances, office machines, household goods, packaging containers, toys, furnitures, synthetic papers and other industrial materials. Because of their atactic configuration in stereochemical structure, however, such styrenic polymers have suffered the disadvantages of inferior heat resistance and chemical resistance.
In order to solve the above-mentioned disadvantages of the styrenic polymers having atactic configuration, the group of the present inventors succeeded in the development of the styrenic polymers having a syndiotactic configuration, and further an arylstyrenic polymer excellent in heat resistance (refer to Japanese Patent Application Laid-Open Nos. 104818/1987, 187708/1987 and 241009/1988, and Japanese Patent Application No. 257484/1990), and still furthermore a silicon-containing styrenic polymer having excellent heat resistance and oxygen enriching capability (refer to Japanese Patent Application No. 201425/1990).
Nevertheless, the above disclosed processes still involve various problems such as expensiveness of the catalyst to be used, insufficient polymerization activity and necessity of deashing process. Specifically a production process by the use of a transition metal compound/aluminoxane catalyst requires a large amount of aluminoxane as compared with a transition metal compound, thus making deashing process indispensable owing to a much content of the residual catalyst in the polymer produced.
Meanwhile, the polymerization of an olefinic monomer by a cationic transition metal complex has been reported since many years ago. For example, (1) Natta et. al reported the polymerization of ethylene using the composition of titanocene dichloride and triethylaluminum as the catalyst (J. Polymer Sci., 26, 120 (1957)). Breslow et. al reported the polymerization of ethylene by the use of titanocene dichloride and dimethylaluminum chloride as the catalyst (J. Chem. Soc, 79, 5072 (1957)). Further, Dyachkovskii et. al suggested that the polymerization activity of ethylene by the use of titanocene dichloride and dimethylaluminum chloride as the catalyst is based on monomethyl titanocene cations (J. Polymer Sci., PART C 16, 2333 (1967)). However, the activity of ethylene according to the above-mentioned methods is extremely low.
In addition, (2) Jordan et. al reported the synthesis of biscyclopentadienylzirconium methyl(tetrahydrofuran)tetraphenyl borate by the reaction of dimethyl zirconocene with silver tetraphenylborate, isolation of the reaction product and the polymerization of ethylene by the use thereof (J. Am, Chem. Soc, 108, 7410 (1986)), and also the synthesis of biscyclopentadienylzirconium benzyl(tetrahydrofuran) tetraphenylborate by the reaction of benzyl zirconocene with ferrocenium tetraphenylborate and isolation of the reaction product (J. Am. Chem. Soc. 109, 4111 (1987)). It was confirmed that ethylene was slightly polymerized by the aforestated catalyst, but the polymerization activity was extremely low.
Moreover, (3) Turner et. al proposed a method for polymerizing .alpha.-olefin by the use of the combination of a boron complex containing a specific amine such as triethylammonium tetraphenylborate, triethylammonium tetratolylborate, triethylammonium tetra(pentafluorophenyl)borate and a metallocene as the catalyst (refer to Japanese Patent Application through PCT Laid-Open No. 502036/1989). However, the aforestated catalyst systems (1) through (3) are applicable only to the restricted polymerization, that is, homopolymerization of an .alpha.-olefin and copolymerization of .alpha.-olefinic comonomers and at the present time, are not actually evolved to the polymerization of a styrenic monomer.